Declaring "our country's going to hell," Republican presidential nominee Donald Trump on Friday pledged to secure the borders, rebuild inner cities and end government corruption during a raucous rally here four days before the election.

Trump boasted of tightening poll numbers in key battleground states as he laid out his vision for the country, which he said would include fixing "inner cities," which he said are "so bad."

"They're unsafe," Trump said. "You get shot walking to the store for a loaf of bread. They have no jobs. I say, 'Give me a chance, I will fix it.' . . . It will be a great thing. We have to fix it."

Trump also knocked Clinton for staging a concert last week in Miami with pop star Jennifer Lopez and for planning another one Friday night in Cleveland with Jay Z, which also is expected to feature his wife, Beyoncé Knowles Carter, according to a person familiar with the details of the event.

"I didn't have to bring JLo or Jay Z," Trump told his large crowd. "I am here all by myself. Just me. No guitar. No piano. No nothing."

Trump appeared earlier Friday in Atkinson, New Hampshire, and Wilmington, Ohio, part of a recent string in rural areas, where he is trying to boost turnout by white working-class voters.

Besides reminding supporters of Clinton's scandals, Trump focused on promises to return lost manufacturing jobs, uplift mitary veterans and protect residents from what he described as dangerous undocumented immigrants.

"Don't let the pundits, the politicians or the media tell you what kind of a country you have," Trump said in Wilmington. "Don't let them limit your dreams because they want to limit your dreams. You can have any future you want."

Clinton, meanwhile, brought a new urgency to her message at a rally earlier Friday in Pittsburgh, focusing on the danger that she said a Trump presidency would present to the country and asking supporters to imagine Trump taking the oath of office in front of the Capitol and being in charge of the nation's nuclear arsenal.

"Think about what it would mean to entrust the nuclear codes to someone with a very thin skin who lashes out at anyone who challenges him," Clinton said. "Imagine how easy it would be that Donald Trump would feel insulted and start a real war, not just a Twitter war at 3 in the morning."

Later, at a rally in Detroit, Clinton talked about issues including criminal justice reform, college affordability and systemic racism, all of which are of particular importance to black voters. She also criticized Trump for portraying the lives of black people as being "all about crime and poverty and despair."

Clinton also dispatched her most potent surrogates around the country Friday. President Barack Obama, Vice President Joe Biden and Sen. Bernie Sanders all stumped for Clinton.

In Denver, former president Bill Clinton talked about everything - from his wife's work on special education to the credit ratings of millennials - assuring around 500 Democrats that they were on track to win.

Obama appeared at a pair of North Carolina rallies, including one Friday night in Charlotte.

"This should not be a close race, but it's going to be a close race," Obams said. "It's going to be especially close in North Carolina. ... We've got to work like our future depends on it, because you know what, our future depends on it."

Earlier in Fayetteville, N.C., Obama continued to assert that Trump is "temperamentally unfit" to be commander in chief and has a long track record of insulting minorities, the disabled, women and others.

"If you disrespected women before you were in office, then you will disrespect women once you take office. If you accepted the support of Klan sympathizers, if you don't denounce them right away because you're not sure, well that's what you're gonna do once you're in office," Obama said.

At Clinton's stop in Pittsburgh, businessman and reality television star Mark Cuban relentlessly needled Trump for potentially not being as wealthy as he claims and for lacking the temperament to be president. Cuban also claimed Trump could be bribed.

"If Donald Trump, who rips off people for thousands, gets offered by some dictator somewhere, some despot somewhere $20 billion, do you think he's going to do what's right for the country or do you think he's going to take the money?" Cuban asked. "Do you think he cares about you or his bank account?"

Trump's surrogates continued to create headaches for his campaign. At the New Hampshire rally, former New Hampshire governor John H. Sununu joked that Clinton's husband does not want to have sex with her.

"Do you think that Bill was referring to Hillary when he said: 'I did not have sex with that woman?' " Sununu said, referring to former president Bill Clinton.

A small crowd gathered at a country club laughed at the joke. One man shouted: "You mean Bill the rapist?" Trump's campaign has yet to respond to the comment.

Sununu was governor of the state in the 1980s and was later White House chief of staff under President George H.W. Bush. He is the father of former senator John E. Sununu and Christopher Sununu, who holds a local office and is running for governor.

While talking about how he plans to win Texas, Trump called the state's agriculture commissioner, Sid Miller, a "wonderful guy." Miller called Clinton the c-word in a tweet.

Also on Friday, two former aides to New Jersey Gov. Chris Christie, who is chairing Trump's transition team, were convicted of all charges related to a plot to create a mammoth traffic jam on the nation's busiest bridge as political retribution. Three people, including the traffic jam's admitted mastermind, testified in federal court that Christie knew about it as it was happening. Christie, on Friday, continued to deny he knew about the plan.

The convictions are a coda to a huge scandal in a state where political misdeeds are as common as the traffic jam that started this one. Known as "Bridgegate," the scheme hobbled Christie as his national star was rising and imperiled his presidential campaign, which ended in February. Since then his approval rating has nose-dived in New Jersey, where only about 20 percent of residents surveyed believe he is doing a good job.

But all of this has had little impact on Christie's standing within the Trump campaign, where the governor is tasked with spearheading Trump's transition to the White House should he win. On Thursday, Christie hosted a $5,000 a person fundraiser for Trump's transition team at a law firm office in Washington.

Clinton campaign chair John Podesta said Christie should step down from the campaign.

"Rather than just crisscrossing the country and hop-scotching, talking about cleaning up the swamp, he might start by draining his own swamp and asking Mr. Christie to resign as the head of his transition," Podesta said of Trump.

At a rally in Ohio, Trump said Clinton should fire Podesta and longtime aide Huma Abedin. The FBI said it found additional emails possibly pertinent to the Clinton investigation on a computer belonging to Abedin's estranged husband, former congressman Anthony Weiner.

Trump's campaign, which has said it will pass massive ethics reform, did not return a request for comment.

Meanwhile, a federal judge on Friday ordered elections boards in three North Carolina counties to restore voter registrations canceled through a so-called "individual challenge law" after the state NAACP sued over thousands of the challenges.

U.S. District Judge Loretta Biggs issued the ruling after an emergency hearing earlier in the week on NAACP allegations that at least three counties purged voter rolls through a process disproportionately targeting blacks.

The ruling could affect several thousand voters in the swing state.